The present invention relates to a siamese type intake passage structure for an internal combustion engine air - fuel mixture intake system, and more particularly relates to such a siamesed type intake passage structure for an internal combustion engine intake system, said internal combustion engine incorporating two intake valves and thus being of the three valve type or the four valve type, wherein there are provided both an intake control valve construction for selectively supplying intake air - fuel mixture to said two intake valves in varying proportions, and also a deflection valve construction in addition to said intake control valve construction.
The present invention has been described in Japanese Patent Application Ser. No. 60-2504222 (1985), filed by an applicant the same as the applicant or the entity assigned or owed duty of assignment of the present patent application; and the present patent application hereby incorporates into itself by reference the text of said Japanese Patent Application and the claim and the drawings thereof; a copy is appended to the present application.
Further, the present inventors wish hereby to attract the attention of the examining authorities to copending patent applications Ser. Nos. 869,890 (now U.S. Pat. No. 4,699,104), 887,658 (now U.S. Pat. No. 4,699,434) and 895,379 (now U.S. Pat. No. 4,671,233), which may be considered to be material to the examination of the present patent application.
In the prior art, there have been proposed various types of intake passage structures for internal combustion engine cylinder heads and intake systems, and in particular for so called siamese type cylinder heads. In Japanese Utility Model Laying Open Publications Ser. Nos. 57-2215 (1982) and 59-123627 (1984), neither of which is it intended hereby to admit as prior art to the present application except to the extent in any case required by applicable law, there is disclosed an internal combustion engine with a so called double or siamesed type intake passage construction, incorporating a generally straight intake passage and a generally helical intake passage arranged in parallel with said generally straight intake passage, so that both said generally straight intake passage and also said generally helical intake passage receive supply of intake air-fuel mixture from the engine intake manifold, with a control valve selectively at least partially interrupting the flow of air-fuel mixture through said straight intake passage, so as selectively to provide extra swirl for the intake air-fuel mixture being sucked into the combustion chamber of the engine, so as to improve the misting of the fuel and in order to increase the intake air-fuel mixture flow speed, thereby to improve the fuel combustibility, the flame front propagation speed, and the firing efficiency, and thereby to militate against engine knocking, thereby to allow the engine to be operated with a weaker intake air-fuel mixture than would otherwise be practicable.
With such an intake passage structure for an internal combustion engine cylinder head and intake system, when the control valve is controlled to be in the closed state by a control system therefor, which is typically done when the current value of engine load is less than a certain determinate threshold value, substantially all of the air-fuel mixture sucked in by the combustion chamber of the engine is inhaled through the generally helical intake passage, and is accordingly imparted with strong swirling. Thus this mode of operation is appropriate for when the engine is operating at low load, as during the idling engine operating condition. In this condition, because of this swirling motion, the limit to which the air-fuel mixture being supplied to the engine can be weakened without engendering deleterious effects is extended. However, at this time the resistance presented to flow of air-fuel mixture by the generally helical intake passage by itself alone is high. On the other hand, when the control valve is controlled to be in the open state by the control system therefor, most of the air-fuel mixture sucked in by the combustion chamber of the engine is inhaled through the generally straight intake passage with only a minor proportion thereof being inhaled through the generally helical intake passage, and accordingly the inhaled air-fuel mixture as a whole is imparted with relatively weak swirling, thus accordingly causing the volumetric efficiency of the engine to be high so as to develop good engine power; this mode of operation is appropriate for when the engine is operating at high load, such as full load. At this time the resistance presented to flow of air-fuel mixture by the combination of the generally straight intake passage and the generally helical intake passage is relatively low.
There is however a problem with such an intake passage structure for an internal combustion engine cylinder head and intake system, in that, when the control valve is thus controlled to be in the closed state by its control system and substantially off of the air-fuel mixture sucked in by the combustion chamber of the engine is being inhaled through the generally helical intake passage and is accordingly being imparted with strong swirling, droplets of fuel tend to stick to the valve member of said control valve, thus causing the amount of fuel supplied to the internal combustion engine combustion chamber or chambers to vary on each engine cycle, so that, particularly when the air/fuel ratio of the overall air-fuel mixture being supplied to the combustion chamber or chambers is near the limit in the weakness direction, the fluctuations of combustion are increased, and thereby the drivability of the engine, and particularly its idling operation, are deteriorated.
When the intake passage control valve is thus in the closed condition, as stated above, the reason for such combustion fluctuations in every engine cycle is because the amount of fuel supplied varies unpredictably, due to droplets of fuel tending to stick to the valve member of said control valve, and these fuel droplets then tend to flow unpredictably and irregularly through the inevitable small gap remaining between the edge of said valve member of said intake passage control valve and the wall of the intake passage against which said valve member edge abuts, thereafter sticking to the wall of the intake passage and oozing in liquid form therealong downstream of the intake control valve, to be thereafter unpredictably and irregularly sucked off from said intake passage wall; at least, this situation is hypothesized by the present inventors.
Now, on the other hand, in Japanese Utility Model Laying Open Publication Ser. Nos. 60- 45829 (1985), which it is not intended, either, hereby to admit as prior art to the present patent application except to the extent in any case required by applicable law, there is disclosed an internal combustion engine, again with a so called double or siamesed type intake passage construction incorporating a generally straight intake passage and a generally helical intake passage arranged in parallel with said generally straight intake passage, so that (similarly to the previous case) both said generally straight intake passage and also said generally helical intake passage receive supply of air from the engine intake manifold, and with a control valve selectively at least partially interrupting the flow of air through said straight intake passage so as selectively to provide extra swirl for the intake air being sucked into the combustion chamber of the engine, but, in this case, with fuel being supplied by a fuel injector into the intake system downstream of said control valve. Thus, since the intake control valve is definitely not provided in the engine intake system downstream of the point at which fuel is supplied to said intake system, the possibility of droplets of fuel adhering to the valve member of said intake control valve and of corresponding increase in the amount of fuel adhering to the walls of the intake passage is of course completely precluded.
However, with this concept of providing the intake control valve upstream of the point at which fuel is supplied into the engine intake system, the problem arises that the effectiveness of the intake control valve for distributing the flow of intake air-fuel mixture between the generally straight intake passage and the generally helical intake passage is deteriorated, and in particular a limit is created to the extent by which air-fuel mixture intake to the combustion chamber or chambers of the engine can be provided only through the generally helical intake passage, and thus, even when the intake control valve is in its fully closed condition, quite a considerably proportion of intake air-fuel mixture inevitably is supplied to the generally straight intake passage. Accordingly in such circumstances, such as in low engine load or idling operational conditions, the swirling of air-fuel mixture within the combustion chamber or chambers is impaired, and the misting of the fuel and also the intake air-fuel mixture flow speed are deteriorated, thereby deteriorating the fuel combustibility, the flame front propagation speed, and the firing efficiency, thus engendering a risk of engine knocking, and preventing the engine from being operated with as weak an intake air-fuel mixture as would otherwise be practicable.
Also, as a subsidiary desideratum for such a siamese type intake passage structure for such an internal combustion engine cylinder head, it is important that, especially during transient driving conditions, the fuel supply responsiveness of the engine should be as good as possible; and this, too, relates to the question of fuel droplets adhering to the walls of the intake passage, as detailed above.